Since passage of the federal Clean Air Act in 1977, air quality standards have been adopted by a growing number of state and local governments. Many such standards limit the amount of volatile organic compounds that may be emitted. Such volatile organic compounds are present in process air used in coating operations, such as in paint spray booths, or printing operations.
Volatile organic compounds were once classified as organic chemical compounds having a vapor pressure in excess of 0.1 mm mercury at standard temperature and pressure (STP). With increasing concern over the deterioration of the protective ozone layer over broad segments of the planet, this definition is being expanded. Volatile organic compounds are increasingly being defined as all hydrocarbons that are photochemically reactive, regardless of the vapor pressure at STP.
There are two control technologies for reduction of volatile organic compounds. They are carbon adsorption and thermal incineration. Adsorption is suitable for applications where the process air has a relatively low solvent concentration. Thermal incineration, in contrast, is suitable for process air that has a relatively high solvent concentration.